Objective To compare survival, life expectancies (LE), and the anticipated age at the time of death (AAD), in a community-based cohort of Parkinson's disease (PD) patients with and without significant cognitive impairment, with an age sex matched population of England and Wales. Methods The age- and sex-specific standardised mortality ratios (SMR) were calculated and stratified by dementia status. The LE and AAD estimations were calculated from the SMRs of the 2003 UK population, using a modified Gompertz function. Results In total, 166 PD patients participated in the investigation, of which 91 died by the 4-year follow-up. The overall SMR was 2.09 (95% CI 1.68 to 2.57). Demented patients had significantly higher SMRs than non-demented patients (SMR 3.10, 95% CI 2.39 to 3.96 vs SMR 1.15, 95% CI 0.75 to 1.69, p75 years), the differences in LE (demented 2.1; SD 1 vs not demented 4.7; SD 4) and AAD were less apparent (demented 89.5; SD 6 vs not demented 92.2; SD 6). Conclusion The survival, LE and AAD in patients with PD are much lower compared with the general population, apart from those patients who do not develop dementia, who appear to have near normal population mortalities. However, dementia and younger onset of PD appear to be important determinants of survival, LE and AAD.